Servo system

ABSTRACT

A master tape movable in a closed loop including a pinch roller transfers a mirror image to a slave tape movable in a closed loop including a capstan. A thermomagnetic layer on the slave tape has a Curie temperature above which magnetic information is destroyed and below which magnetic information can be recorded on such layer. The thermomagnetic layer is heated above the Curie temperature, thereby becoming lengthened by thermal expansion just before the slave tape reaches the capstan. A downstream portion of a peripheral surface, preferably defining a cylindrical segment, on a first guide receives a pressurized fluid for sensing the tape tension in accordance with the tape width, distance from the cylinder axis and fluid pressure. An upstream portion of the guide peripheral surface receives a vacuum adjustable to regulate tape tension in response to variations in the pressurized fluid pressure. In regulating the tape tension, the spacing between the slave tape and the peripheral surface at the downstream portion is controlled. The master tape is lengthened by a second guide having the same construction as the first guide to compensate for the slave tape lengthening by the heater and the first guide, thereby producing a mirror image on the slave tape after the slave tape has cooled to the ambient temperature. Each of the master and slave tapes has a particular product of the Youngs modulus, tape width and tape thickness to provide a controlled strain on such tape when the tension on such tape is regulated.

This is a division of application Ser. No. 07/886,688 filed May 19, 1992(now U.S. Pat. No. 5,392,976).

This invention relates to apparatus for, and methods of, transferringvisual and audio information on a master tape to a slave tape. Moreparticularly, this invention relates to apparatus for, and methods of,transferring visual and audio information in magnetic form on a mastertape to a thermomagnetic layer on a slave tape. The invention alsorelates to a master or slave tape with properties individual to theapparatus and methods of this invention.

Visual and audio information is often stored on a tape for playback at asubsequent time. For example, visual and audio information relating topopular motion pictures is stored on tapes. These tapes are rented orsold at neighborhood stores. A popular movie such as "Batman" or a moviewinning an Academy Award has millions of taped copies distributed tosatisfy the demands of purchasers and renters. Substantially all ofthese taped copies have to be made available at a pre-selected releasedate in order to satisfy the pent-up demand of viewers for such tapedcopies. Although the demand for movie rentals and sales is great, thedemand still seems to be increasing significantly from year to year.

Visual and audio information on tapes is not only provided in the formof movies for entertainment. It is also provided in large volume forbusiness purposes. For example, large corporations deliver messages inthe form of tapes to their sales personnel to acquaint such salespersonnel with the construction, operation and advantages of newproducts. Since large corporations employ large numbers of sales copies,many copies of such messages have to be prepared for distribution totheir sales personnel.

The visual and audio information on most tapes is in magnetic form. Onereason is that information in magnetic form can be relatively easily andinexpensively reproduced. For example, most reproducing apparatus in thehome use magnetic heads to read the information recorded magnetically onthe tapes when the tapes are inserted into such apparatus. Anotherreason is that tapes with information recorded in magnetic form are lessexpensive to reproduce than tapes in other forms such as in opticalform.

One type of tape for recording information in magnetic form has athermomagnetic layer on the tape. The thermomagnetic layer may be formedfrom a suitable material such as chromium dioxide. The thermomagneticlayer has a Curie temperature at or above which any magnetic informationon the tape is destroyed and below which magnetic information can berecorded on the tape. Thermomagnetic tape is advantageous becauseinformation can be recorded on the thermomagnetic tape at a temperatureat or somewhat above the Curie temperature by pressing a master tapeagainst the thermomagnetic layer on the slave tape at such atemperature. This causes the surface of the thermomagnetic layer tobecome cooled to a temperature below the Curie temperature by contactwith the cool surface of the master tape. As the thermomagnetic layercools to a temperature below the Curie temperature, the magneticinformation on the master tape becomes transferred to the thermomagneticlayer on the slave tape. The information on the master tape thus becomestransferred in mirror form to the thermomagnetic layer on the slave tapewithout having to use any magnetic heads to write information on theslave tape.

There is at least one apparatus now in use for transferring informationin magnetic form on a master tape to a thermomagnetic layer on a slavetape. Although this apparatus is fast, it is large, cumbersome andexpensive, and it requires excessive electrical power. It is accordinglynot economical to transfer images from a master tape to a slave tape byusing the apparatus.

With the millions of copies that have to be made of a single movie suchas the movie winning an Academy Award, it would be desirable to provideapparatus which is relatively inexpensive and which transfersinformation from a master tape to a slave tape in a minimal period oftime and with low consumption of power. For example, it would bedesirable to provide equipment which sells at most for a few thousanddollars and which reproduces a two (2) hour movie in approximatelythirty (30) to sixty (60) seconds without any need for using magneticreproducing heads. Because of the desire, and actually the need, forsuch apparatus, a considerable effort has been devoted, and asignificant amount of money has been expended, to develop apparatuswhich meets such criteria. In spite of such effort and such moneyexpenditure, no satisfactory apparatus meeting such criteria has beenprovided to this date.

Co-pending application Ser. No. 733,174 filed by Alfred M. Nelson andRobert P. Adams on Jul. 19, 1991, for a "Tape Duplicating System"provides apparatus which more than meets the criteria specified in theprevious paragraph. It is able to record a two (2) hour movie inapproximately thirty (30) to sixty (60) seconds such that the duplicatedcopy has the visual and audio fidelity of the original or master copy.It is compact so that it occupies relatively little space. This isimportant when a large number of apparatuses are used simultaneously inan enclosure such as a room to make duplicate copies. For example, theapparatus can be used to transfer the information on a master-mastertape to a master tape, and subsequently the same apparatus can be usedto transfer the information on the master tape to the slave tape, allwithout using recording heads. The apparatus also consumes low amountsof power.

In the apparatus disclosed and claimed in co-pending application Ser.No. 733,174, a master tape moves between first supply and take-up reelsover a pinch roller. A slave tape moves between second supply andtake-up reels over a capstan. First and second guides can berespectively constructed and adjustably positioned to regulate themovement of the master and slave tapes to aligned positions on the pinchroller and the capstan. A heater disposed between the capstan and thesecond guide heats only a thermomagnetic layer on the slave tape to atleast the Curie temperature. The heater is adjustable in position tofacilitate the movement of the slave tape to the aligned position on thecapstan. A brake shoe between the capstan and the second supply reelcontrols the tape tension and damps any variations in the tension of theslave tape. A second brake shoe between the pinch roller and the firstsupply reel controls the tape tension and damps any variations in thetension of the master tape.

The pinch roller is movable to a first position and locked in positionrelative to the capstan, in which it abuts the capstan to facilitate thetransfer of magnetic information from the master tape to the slave tape.In this disposition, the pinch roller locks the heater in a fixedposition relative to the capstan. The pinch roller and the associatedguide are movable to a second position displaced from the capstan tofacilitate the disposition of the master tape on the pinch roller. Theheater is pivotable relative to the capstan to facilitate thedisposition of the slave tape on the capstan. The capstan, preferably ofa unitary construction, receives forces to maintain the capstanrotational axis substantially constant.

Since the tapes pass over surfaces between the brake shoes and thecapstan and the pinch roller, the tensions on the master and slave tapesare not as closely regulated at the position of transfer of the magneticinformation from the master tape to the slave tape as might otherwise bedesired. Specifically, the tapes pass over alignment guides which have avariable friction with time and physical conditions. This variablefriction inhibits a precise regulation of the tape tensions at theabutting positions between the capstan and the pinch roller where themagnetic information is transferred to the slave tape.

In one embodiment of the invention, a master tape movable in a closedloop including a pinch roller transfers a mirror image to a slave tapemovable in a closed loop including a capstan. A thermomagnetic layer onthe slave tape has a Curie temperature above which magnetic informationis destroyed and below which magnetic information can be recorded onsuch layer. The thermomagnetic layer is heated above the Curietemperature, thereby becoming lengthened by thermal expansion justbefore the slave tape reaches the capstan.

A downstream portion of a peripheral surface, preferably defining acylindrical segment, on a first guide receives a pressurized fluid forsensing the tape tension in accordance with the tape width, distancefrom the cylinder axis and fluid pressure. An upstream portion of theguide peripheral surface receives a vacuum adjustable to regulate tapetension in response to variations in the pressurized fluid pressure.

In regulating the tape tension, the spacing between the slave tape andthe peripheral surface at the downstream portion is controlled. Themaster tape is lengthened by a second guide having the same constructionas the first guide to compensate for the slave tape lengthening by theheater and the first guide, thereby producing a mirror image on theslave tape after the slave tape has cooled to the ambient temperature.

Each of the master and slave tapes has a particular product of theYoungs modulus, tape width and tape thickness to provide a controlledstrain on such tape when the tension on such tape is regulated.

This invention provides apparatus for, and methods of, regulating thetension of a master tape at a position contiguous to a pinch roller andfor regulating the tension of a slave tape at a position contiguous to aheater, which is in turn contiguous to a capstan. The apparatus andmethod of this invention are adapted to be used in the apparatus andmethod of co-pending application Ser. No. 733,174 and to constitute animprovement in the apparatus and method of copending application Ser.No. 733,174. The invention also provides a master tape and a slave tapewhich may be constructed especially for the apparatus and method of thisinvention to obtain all of the advantages provided by the apparatus andmethod of this invention.

In the drawings:

FIG. 1 is a schematic plan view, partly in block form, of one embodimentof apparatus for transferring the information, preferably in magneticform, on a master tape to a slave tape;

FIG. 2 is an enlarged perspective view of a portion of the apparatusshown in FIG. 1 and illustrates this portion of the apparatus inadditional detail, this portion including the members adjacent to andincluding the position where the information on the master tape istransferred to the slave tape;

FIG. 3 is an enlarged perspective view of braking apparatus associatedwith a supply reel or cassette (also shown in FIG. 1) for controllingthe unwinding of a tape from the supply reel;

FIG. 4 is an enlarged plan view of a guide means (also shown in FIG. 1)for regulating the tension of the tape at a position contiguous to apinch roller which receives the master tape and provides for a mirrortransfer of the image on the master tape to a slave tape;

FIG. 5 is an enlarged sectional view of apparatus associated with theguide means shown in FIG. 4 for operating in conjunction with theapparatus shown in FIG. 4 for regulating the tension on the master tapeat the position contiguous to the pinch roller;

FIG. 6 is an enlarged schematic elevational view of the external surfaceof the guide means (also shown in FIG. 1, 4 and 5) associated with themaster tape;

FIG. 7 is an enlarged schematic elevational view of the external surfaceof the guide means (also shown in FIG. 1) associated with the slavetape, the guide means associated with the slave tape being constructedin a manner similar to the construction of the guide means associatedwith the master tape;

FIG. 8 is an enlarged perspective view of a portion of the apparatusincluded in FIG. 1 and specifically illustrates the construction of aguide pin, the guide means shown in FIGS. 4 and 6 and a pinch roller andthe disposition of these members in the path of movement of the mastertape;

FIG. 8A is an enlarged perspective view of the external surface of theguide means shown in FIG. 8;

FIG. 9 is an enlarged fragmentary sectional view taken substantially onthe line 9--9 of FIG. 8 and illustrates in additional detail theconstruction of the guide means for the master tape at the input end ofthe guide means in the direction of movement of the master tape;

FIG. 10 is an enlarged fragmentary sectional view taken substantially onthe line 10--10 of FIG. 8 and illustrates additionally the constructionof the guide means;

FIG. 11 is an enlarged fragmentary sectional view taken substantially onthe line 11--11 of FIG. 8 and illustrates in further detail theconstruction of the guide pin for the master tape in the direction ofmovement of the master tape;

FIG. 12 is an enlarged perspective view of the pinch roller and theguide means, as seen from a position above and to one side of suchmeans, for receiving the master tape, the pinch roller being disposed ina position withdrawn from an abutting relationship with a capstan;

FIG. 12A is an enlarged perspective view of the pinch roller and guidemeans shown in FIG. 12 as seen from a position below and to the otherside of such means with the pinch roller and the guide means in thewithdrawn position;

FIG. 12B is an enlarged elevational view of the pinch roller and theguide means with the pinch roller and the guide means in the extendedposition;

FIG. 13 is an enlarged, partly exploded, perspective view of the pinchroller and the guide means with the pinch roller and the guide means inthe withdrawn position;

FIG. 14 is an enlarged fragmentary sectional view taken substantially onthe line 14--14 of FIG. 13 and illustrates a bearing assembly associatedwith the pinch roller for assuring that the pinch roller does not rotatein an off-round relationship;

FIG. 15 is an enlarged exploded perspective view of the pinch roller andthe guide means shown in FIGS. 12-14 and of the capstan assembly, asseen from a position above and to one side of these members, with thepinch roller and the guide means in the extended relationship shown inFIG. 18;

FIG. 16 is an enlarged perspective view of the capstan assembly, as seenfrom a position above and to the other side of the capstan assembly;

FIG. 17 is an enlarged perspective view of the pinch roller and theassociated guide means and of the capstan assembly, as seen from aposition above and in front of these members, when the pinch roller andthe guide means have been extended almost to the position of the pinchroller abutting the capstan;

FIG. 18 is an enlarged perspective view of the pinch roller and theassociated guide means and the capstan assembly, as seen from a positionabove and in front of these members, when the pinch roller and the guidemeans have been extended to the position of the pinch roller abuttingthe capstan;

FIG. 19 is an enlarged fragmentary sectional view taken substantially onthe line 19--19 of FIG. 18 and illustrates the construction of anassembly for providing for the movement of the pinch roller and theassociated guide means between the withdrawn and extended positions;

FIG. 20 is an enlarged perspective view of the capstan assembly andassociated members, including associated guide means, for guiding themovement of the slave tape to the capstan, the view being provided froma position above and to one side of these members;

FIG. 21 is an enlarged perspective view of the capstan assembly and theassociated members, including the associated guide means shown in FIG.20, as seen from a position above and to the other side of thesemembers, and also shows a disposition of the slave tape on thesemembers;

FIG. 22 is an enlarged perspective view of a heater assembly including aheater for heating the thermomagnetic layer on the slave tape to atemperature above the Curie temperature just before the slave tapereaches the capstan, the view being taken from a position above and toone side of the heater assembly;

FIG. 23 is an enlarged perspective view of the heater assembly and thecapstan assembly and the associated guide means as seen from a positionabove and to the other side of the heater assembly and furtherillustrates the disposition of the slave tape on the guide means, theheater and the capstan;

FIG. 24 is an enlarged fragmentary sectional view taken substantially onthe line 24--24 of FIG. 22 and illustrates the construction of the pivotassembly for pivoting the heater assembly between a position with theheater receiving the slave tape and a withdrawn position and furtherillustrates the members for tilting the heater assembly relative to thecapstan;

FIG. 25 is an enlarged fragmentary sectional view taken substantially onthe line 25--25 of FIG. 24 and illustrates in additional detail theconstruction of the members for tilting the heater assembly relative tothe capstan;

FIG. 26 is an enlarged fragmentary view taken substantially on the line26--26 of FIG. 24 and illustrates in further detail the construction ofthe members for tilting the heater assembly relative to the capstan;

FIG. 27 is an enlarged sectional view taken substantially on the line27--27 of FIG. 22 and illustrates the heater and the construction ofmembers for holding the heater in a fixed position on the heaterassembly;

FIG. 28 is a schematic perspective view illustrating the disposition ofthe slave tape on the heater;

FIG. 29 is an enlarged fragmentary perspective view of the heater andillustrates additional details concerning the construction of theheater;

FIG. 30 is a perspective view of the heater for instantaneously heatingthe thermomagnetic layer on the slave tape to a temperature above theCurie temperature;

FIG. 31 is an enlarged fragmentary sectional view taken on the line31--31 of FIG. 30 and illustrates the different layers of material whichare disposed on an electrically insulating support member to form oneembodiment of the heater;

FIG. 32 is an enlarged sectional view taken substantially on the line32--32 of FIG. 31 and illustrates additional details of the embodimentof the heater shown in FIG. 31;

FIG. 33 is an enlarged fragmentary sectional view corresponding to theview shown in FIG. 31 and illustrates a modification of the heater shownin FIG. 31;

FIG. 34 is an enlarged fragmentary sectional view taken substantially onthe line 34--34 of FIG. 30 and illustrates a modification to theembodiment shown in FIG. 31;

FIG. 35 is an enlarged fragmentary plan view of the pinch roller, thecapstan, the guide means associated with the capstan, and the heaterassembly in the operative positions of these members;

FIG. 36 is an enlarged fragmentary view, partly in section, of theportion of the members shown in FIG. 35 within a broken circledesignated by the numeral "36" in FIG. 35;

FIG. 37 is an enlarged fragmentary sectional view taken substantially onthe line 37--37 of FIG. 35 and illustrates a portion of the pinch rollerand the capstan and the master and slave tapes with the master and slavetapes in abutting relationship to each other and to the pinch roller andthe capstan;

FIG. 38 is a fragmentary sectional view, enlarged with respect to FIG.37, of the portion of the members within the broken circle designated bythe numeral "38" in FIG. 37 and particularly illustrates the abuttingrelationship of the magnetic layer on the master tape and thethermomagnetic layer on the slave tape;

FIG. 39 is a schematic block diagram of a system for regulating the heatproduced by the heater for the thermomagnetic layer on the slave tapeand for providing a rapid heating of the heater on a regulated basiswhen the apparatus shown in the previous Figures initially becomesoperative;

FIG. 40 provides a curve illustrating the relationship between tapetension and a parameter such as a sensor voltage for presetting theapparatus shown in FIG. 5 to regulate the tension on the guide meansshown in FIG. 4;

FIG. 41 schematically illustrates the disposition of the master tape onthe periphery of the guide means shown in FIG. 4 when the tension of thetape has been regulated to a preselected value,

FIG. 42 provides a curve showing the relationship between the flow ofair under pressure to the periphery of the guide means shown in FIG. 4and the pressure of the air providing such flow; and

FIG. 43 is a schematic diagram, partly in block form, of apparatus fordetermining the characteristics of a tape (either master or slave) andfor setting the constraint of a spring shown in FIG. 5 to provide aparticular strain or tension on the master or slave tape during theprocess of transferring information from the master tape to the slavetape.

The apparatus of this invention is intended to constitute an improvementof the apparatus disclosed and claimed in co-pending application Ser.No. 733,174. Many of the drawings of this application are identical, orsubstantially identical, to corresponding drawings in co-pendingapplication Ser. No. 733,174. Because of this, if there is anydeficiency in the drawings or disclosure of this application, thedrawings and disclosure of co-pending application Ser. No. 733,174 areintended to complete the disclosure of this application.

In one embodiment of the invention, a master tape 10 (FIG. 1) isprovided with a mirror image of information such as visual pictures andaural sound to be produced on a slave tape 12. Preferably the mirrorimage of the visual and aural information is recorded in magnetic formon the master tape 10. The mirror image may be recorded in either analogor digital form. The visual and aural information may be provided in alayer 11 (FIG. 38) of a magnetizable oxide such as an iron oxide on thesurface of the backing member of the master tape. The magnetizable oxide11 may be formed in a conventional manner on the master tape 10.

A slave tape 12 (FIGS. 1 and 38) preferably has a thermomagnetic layer14 (FIG. 38) on the tape. The thermomagnetic layer 14 may be formed onthe backing member of the slave tape 12 from a suitable material such aschromium dioxide in a manner well known in the art. The thermomagneticlayer 14 preferably has a Curie temperature above which magneticinformation in the thermomagnetic layer is destroyed and below which themagnetic information on the master tape can be duplicated in the mirrorimage on the thermomagnetic layer 14 on the slave tape. Preferably theduplication occurs at a temperature close to, but below, the Curietemperature. When this occurs, the duplication can occur by pressing themaster and slave tapes together and can occur without any need toprovide magnetic heads for recording the magnetic information from themaster tape 10 on the slave tape 12. It will be appreciated that themagnetic layer 11 on the master tape 10 may also be formed from athermomagnetic material.

As will be described, one of the features of this invention is that thetension of the master tape and the tension of the slave tape arerespectively regulated at particular values at positions respectivelynear the positions where the information on the master tape istransferred in a mirror image to the slave tape. Another feature of thisinvention is that each of the master tape and the slave tape is providedwith particular characteristics so that the strain (the elongation ininches per inch) on each slave tape is maintained at a first particularvalue and the strain on each slave tape is maintained at a secondparticular value. These strains are chosen so that a precise image isrecorded by each master tape in a mirrored form on each slave tape whenthe slave tape has cooled to an ambient temperature. This provides foran accurate playback of the image on a VCR machine with a highresolution.

The master tape 10 can be initially wound on a supply reel or cassette16 and can then be unwound from the supply reel or cassette 16 and woundon a take-up reel or cassette 18. The unwinding of the master tape 10from the cassette 16 by a capstan motor 123 (FIG. 1) and the winding ofthe master tape on the cassette 18 can occur through the operation of atake-up motor 20 (FIG. 1). The cassettes 16 and 18 and the take-up motor20 can be constructed in a conventional manner as in a video cassettereproducer found in many homes. Similarly, a supply reel or cassette 22,a take-up reel or cassette 24 and a take-up motor 26 can be provided forthe slave tape 12.

An annular control member 28 (FIGS. 1 and 3) is disposed in a concentricrelationship with the cassette 16 on a shaft 30. A strap 32 is woundpartially around the annular control member 30 and is attached at oneend as at 34 to a mechanical ground. At the other end, the strap 32 isattached to an intermediate position on a rod 36 which is pivotable atone end as at 38. At its other end, the rod 36 has a pin 40. Theconstruction and arrangement of the annular control member 28, the shaft30, the strap 32 and the rod 36 are well known in the art of videocassette recording and reproducing equipment. A similar arrangement mayalso be provided in association with the supply reel or cassette 22.

The master tape 10 extends from the cassette 16 over a pin 42, the pin40 on the rod 36, a pin 44, a post 46 (FIG. 1) and a guide pin 48 (FIGS.1, 8, and 11) to the peripheral surface 50 of an alignment guidegenerally indicated at 52. The peripheral surface 50 of the alignmentguide 52 is inclined at a small angle (FIG. 9) at its upstream end. Thissmall angle causes the tape to ride down to ledge 53, thus accuratelyaligning the tape to the ledge height. The guide pin 48 is tilted toprovide compensation for the differential strain introduced by theinclined surface 50 of the alignment guide 52. The optimum tilt angle isa function of the wrap angle, the tension of the tape, and the slope ofthe alignment guide 52. If the tilt is too large, the tape will rideupwardly off the ledge of the alignment guide at the input end. If thetilt is too small, excessive force will be created on the tape edge.This can result in a buckling of the tape at the input end of thealignment guide 52 and wear of the ledge 53.

At the downstream end of the guide 52, the slope of the guide face onthe alignment guide 52 transitions to a perpendicular relationship withthe pinch roller. This is indicated at 55 in FIG. 10. Thus the tapeexits the guide in a plane parallel to the pinch roller axis and withoutdifferential strain. The inclined surface 50 and the perpendicularsurface 55 are undercut as at 54 (FIGS. 8A, 9 and 10) to assure that thetape will have a planar disposition along the inclined and perpendicularsurfaces.

The guide 52 may be hollow and may be provided with an internal wall asat 56 at an intermediate position to define a pair of isolated chambers57 and 58 (FIG. 4). The chamber 57 is upstream from the chamber 58 inthe direction of movement of the master tape 10. The guide 52 may beprovided with a pair of peripheral surfaces 59 and 60 which arecontinuous with each other. Preferably the peripheral surfaces 59 and 60define a segment of a cylinder for advantageous reasons which willbecome apparent subsequently. Orifices 61 communicate the chamber 57with the peripheral surface 59 and orifices 62 communicate the chamber58 with the peripheral surface 60. A variable vacuum is produced in thechamber 57 and a fluid (e.g. air) under a variable pressure isintroduced to the chamber 58. The variable vacuum may be produced by avacuum source 59a (FIGS. 1 and 5) and the air under pressure may beobtained from a source 60a (FIGS. 1 and 5). A reservoir 61b and anorifice 61a may be disposed between the vacuum source 59a and thechamber 57. Similarly, a reservoir 62 and an orifice 62a may be disposedbetween the source 60a and the chamber 58.

The variable vacuum in the chamber 57 and the variable pressure aboveatmospheric pressure in the chamber 58 are produced by the valvingmechanism generally indicated at 63 in FIG. 5. The valving mechanism 63includes a tube 64 closed at one end (e.g. the upper end) in FIG. 5. Aconstraining member such as a spring 66 is attached at one end to theclosed end of the tube 64 and at the other end to a rod 65. The spring66 constrains the rod 65 for movement in an upward direction. Anarrangement including a screw 67 and an adjustable nut 68 are providedat the closed end of the tube 64 to adjust the constraint on the spring66. The upper end of the spring 66 is attached to the bottom end of thescrew 67 to provide for the adjustment in the constraint of the springwhen the screw 67 is turned in the nut 68.

Air under a variable pressure is introduced through a conduit 68 fromthe source 60a of pressurized air to a first chamber 69 which may beisolated from the tube 64. An extension 65a of the rod 65 extendsthrough the chamber 69 and through a resilient diaphragm 70 in sealedrelationship to the chamber 69. The diaphragm 70 is coupled to the rod65 for movement upwardly and downwardly in accordance with the movementof the piston. The diaphragm 70 defines one end of a second chamber 71which receives air at atmospheric pressure through a conduit 72. Theopposite end of the chamber 71 is defined by a resilient diaphragm 73which is sealed to a piston 73a for movement with the piston. The piston73a is suitably attached to the rod extension 65a.

A variable vacuum is introduced from the vacuum source 59 through aconduit 74 to a third chamber 75 which is isolated from the secondchamber 71 by the resilient diaphragm 73. The vacuum chamber 75 is openat one end (e.g. the bottom end in FIG. 5) to define a valve seat 76. Avalve rod 77 preferably having a conical configuration defines with thevalve seat 76 a valve having a variable leakage to the atmosphere inaccordance with the vertical positioning of the valve rod relative tothe valve seat. The valve rod 77 constitutes an extension of the piston65.

The spring 66 is provided with characteristics to produce a particulartension on the master tape 10 as the master tape moves along theperipheral surface 60 (FIG. 4) of the guide 52. This tension provides adisplacement of the master tape 10 from the peripheral surface 60 of theguide 52. This is indicated by the distance AR in FIG. 41. The magnitudeof this tension determines the radial distance R+ΔR of the displacementof the tape 10 from the axis of the peripheral surface 60 of the guide52. As the radial distance AR between the master tape 10 and theperipheral surface 60 of the guide 52 increases, an increased amount ofthe air under pressure is able to escape from the chamber 58 through theorifices 62 and into the atmosphere through the space between the mastertape 10 and the peripheral surface 60 of the guide 52. This causes thepressure of the air passing from the source 60 of pressurized airthrough the conduit 68 to the chamber 69 (FIG. 5) to decrease.

The decreased pressure of the air in the chamber 69 (FIG. 5) causes theforce exerted downwardly by the air in the chamber 69 to decrease.Because of this, the force exerted upwardly by the spring 66 on the rod65 becomes dominant so that the rod is moved upwardly in FIG. 5. Thiscauses the opening between the valve rod 77 and the valve seat 76 todecrease such that an increased vacuum is produced in the chamber 75.This increased vacuum results only from the force of the spring 68 sincethe force exerted downwardly on the rod 65 by the diaphragm 73 is equaland opposite to the force exerted upwardly on the rod 77 by theatmospheric pressure below the rod. This results from the fact that thearea of the diaphragm 73 is equal to the area of the valve seat 76. Thisincreased vacuum is also introduced to the chamber 57 in FIG. 4.

The increased vacuum in the chamber 57 (FIG. 4) produces an increasedforce on the master tape 10 in a direction to position the tape firmlyon the peripheral surface 59 of the guide 52 as the tape moves on suchperipheral surface. This increased force produces an increased frictionbetween the master tape 10 and the peripheral surface 59 of the guide52. The tape 10 is pulled at a constant speed by a capstan 160 inproximity with a pinch roller 100 (FIG. 18) and the increased frictionof the tape with respect to the peripheral surface causes an increasedtape tension. This increased tension on the master tape 10 produces adecrease in the spacing between the master tape 10 and the peripheralsurface 60 of the guide 52. The decreased spacing between the mastertape 10 and the peripheral surface 60 of the guide 52 provides for anincrease in the pressure of the fluid passing from the source 60a ofpressurized air through the conduit 68 to the chamber 69 in FIG. 5.

The increased pressure of the fluid in the chamber 69 results in adownward movement of the rod 65 to open the valve defined by the rod 77and the valve seat 76. The opening of this valve causes the vacuumintroduced to the chamber 57 to decrease, thereby decreasing thefrictional force produced on the master tape 10 on the peripheralsurface 59 of the guide 52. In this way, the tension of the master tape10 is regulated at a value dependent upon the constraint provided by thesetting of the spring 66.

As will be seen from the above discussion, the tape tension sensor maybe considered to be produced by an air bearing between the tape 10 andthe peripheral surface 60 of the tape. Since the tape 10 does not touchthe peripheral surface 60 of the guide 52, there is no frictionalretarding force on the tape 10 as the tape moves along this peripheralsurface. The tape tension sensed is accordingly a true representation.The variables affecting the pressure sufficiently only to lift the tape10 slightly from the peripheral surface 60 may be intuitively, but notvigorously, seen from the following analysis.

The air pressure sufficient in the tape sensor to lift the tape 10slightly from the peripheral surface 60 is proportional to the tapetension since the normal force caused by the tape tension must beovercome linearly by the air pressure. The air pressure sufficient tolift the tape 10 is inversely proportional to the area of the tape incontact with the tape tension sensor since an air pressure over anincreased area will overcome an increased normal force (and hence tapetension).

If the convex surface receiving the tape 10 is a section of a cylinder(as is the peripheral surface 60 in FIG. 4), the area of the tape 10 incontact with the tape tension sensor is proportional to the radius ofthe cylindrical segment defined by the peripheral surface 60 of theguide 52 (because the radius of the cylindrical segment is proportionalto the circumference of the cylindrical segment and the tape width isconstant). Furthermore, the area of the tape 10 is proportional to thewidth of the tape.

In view of the above,

    V=KT/WR, where                                             (1)

P=the air pressure at the peripheral surface 60;

K=a constant;

T=the tension of the tape 10 at the peripheral surface 60;

W=the width of the tape 10;

R=the radius defined by the tape 10 with respect to the axis of thecylindrical configuration of the peripheral surface 60

The constant K happens to be equal to the integer "1".

Solving for T in equation (1)

    T=PRW                                                      (2)

Thus, the tension of the tape 10 is proportional to the product of thewidth of the tape 10, the radius of the tape with respect to the axis ofthe peripheral surface 60 of the guide 52 and the air pressure at theperipheral surface 60. As previously described, the air pressure isdependent upon the spacing between the tape 10 and the peripheralsurface 60 of the guide 52.

The following is a more vigorous analysis to determine the tension T ofthe master tape 10 than that specified above in equations (1) and (2).Assume that the tension sensor has the shape of a cylinder with a radiusR and the tape 10 rides over a sector (in radius) of the cylindricalsurface defined by the tape sensor. Assume also that there is a chamberwithin this cylindrical surface and that this chamber (e.g. the chamber58 in FIG. 4) has a pneumatic pressure which is positive with respect toatmospheric pressure. Assume further that there are a multiplicity oforifices (e.g. the orifices 62 in FIG. 4) communicating between thechamber (e.g. the chamber 58) and the peripheral surface (e.g. thesurface 60) and that all of these orifices are under the tape 10.

On the basis of the assumptions in the previous paragraph, for aparticular tape tension T, there is within the chamber (e.g. the chamber58) a particular pressure P which will lift the tape slightly above thecylindrical surface (e.g. the surface 60). This slight distance can bedesignated as ΔR as shown schematically in FIG. 41. This increase ΔR inthe radial distance of the tape 10 from the peripheral surface 60 of theguide 52 causes an increase ΔL to occur in the length of the tape 10over the sector φ defined by the peripheral surface 60. Then the energyrequired to move the tape 10 the distance ΔL against the action of thetape tension T equals the energy required to increase the volume of airby the increment ΔV under the tape 10 at an air pressure P.

The relationship discussed in the previous paragraph can be expressed as

    TΔL=PΔV                                        (3)

The increase ΔL in the length of the tape 10 over the sector B can beexpressed as

    ΔL=β(R+ΔR)-βR                        (4)

where β is the angle of tape rap over the sector expressed in radians.Equation (4) can be simplified to

    ΔL=BΔR                                         (5)

ΔV can be expressed as

    ΔV= Wπ(R+ΔR)(R+ΔR)(B/(2π))!- WπRR(β/(2π))!                                                         (6)

Equation (6) indicates the difference in volume over the sector for aradius (R+ΔR) and for a radius (R). Equation (6) can be simplified to

    ΔV=Wβ(RΔR+ΔRΔR)               (7)

If R is assumed to be considerably greater than ΔR/2 equation (7) can besimplified to

    ΔV=WβRΔR                                  (8)

Substituting in equation (8) the value of ΔV obtained from equation (3),

    (TΔL)/P=WβRΔR                             (9)

Substituting equation (5) in equation (9),

    (TβΔR)/P=WβRΔR                       (10)

Equation (10) may be simplified and transposed to obtain

    T=WRP                                                      (11)

As will be seen, equation (11) from a rigorous analysis corresponds toequation (2) from a simplified analysis. In accordance with equation 11,the tension of the tape 10 is equal to the product of the width of thetape, the radius of the tape to the axis of the peripheral surface 60 ofthe guide 52 and the pressure of the air at the peripheral surface 60.

FIG. 40 illustrates the relationship between the sensor voltage used topreset the spring 65 and the tension of the master tape 10 in pounds.This relationship is used to preset the compression of the spring 65 sothat a proper tension is applied to the master tape 10 to obtain anoptimal operation of the system of this invention. There is a tendencyto preset the tension of the spring 65 to the middle of the range shownin FIG. 40.

FIG. 42 illustrates the relationship between the flow of air underpressure through the orifices 62 in the peripheral surface 60 of theguide 52 and the pressure of such air. The flow is shown along thehorizontal axis and is in pounds per second times one thousand (#10³/sec). The pressure is in inches of mercury (in-Hg). There is a tendencyto provide the setting in the middle of the range shown in FIG. 42.

As will be appreciated, it would be desirable not to have to change theset point for the tension of the master tape 10 with each new batch ofmaster tape. This may be accomplished as shown by the followinganalysis. The cross sectional area of the tape 10 is the width W of thetape multiplied by the thickness of the tape. The tension of the mastertape 10 divided by the cross sectional area of the tape constitutes thestress S on the tape 10. The stress S equals a constant E (constitutingthe Youngs Modulus) times the strain e, which is equal to the change inthe length of the tape 10 divided by the length of the tape.

The requirements for manufacturing the master tape 10 can be computed asfollows: As will be seen from the previous paragraph,

    S=Ee, where                                                (11)

S=the stress on the tape 10;

E=the Youngs Modulus of the tape 10; and

e=the strain on the tape 10.

The stress S on the tape 10 can also be written as

    S=T/Wd, where                                              (12)

T=the tension of the tape 10;

W=the width of the tape 10; and

d=the thickness of the tape 10.

By substituting equation (12) in equation (11)

    Ee=T/Wd                                                    (13)

Solving equation (13) for the strain e on the tape 10,

    e=T/WdE                                                    (14)

In order to maintain the set point for the tension of the master tape 10substantially constant, the manufacturer of the master tape 10 has tomaintain the strain e substantially constant. Thus, the manufacturer hasto maintain the product EWd substantially constant. In other words, themanufacturer has to maintain the product of the width, thickness andYoungs modulus of the master tape 10 substantially constant. The width Wof the tape 10 is generally maintained substantially constant for otherreasons. For example, it is desirable to maintain the width W of themaster tape 10 substantially constant so that in some prior artduplicators the master tape will be positioned properly on the capstanwhen the mirror image is transferred from the master tape 10 to theslave tape 12. If the width W of the master tape 10 is maintainedsubstantially constant, the manufacturer of the master tape 10 has tomeet the following requirement:

    Ed=a constant                                              (15)

Applicants believe that a tape meeting these requirements has never beenprovided in the prior art and that, accordingly, a tape meeting theserequirements is patentable.

The Youngs modulus of the master tape 10 may be varied by heating thetape 10 to an elevated temperature below the temperature at which thetape loses its shape. The tape is then stretched longitudinally and/orlaterally. The stretching may be provided progressively in successiveoperations with each operation providing additional stretching. Theamount of tape stretching in the longitudinal and lateral directionscontrols the Youngs modulus of the tape longitudinally and laterally. Itis known in the prior art to stretch tapes longitudinally and laterallyto control the Youngs modulus of the tape. The thickness of the tape canbe controlled by varying the aperture of the extrusion. It is known inthe prior art to control the thickness of the tape.

The guide 52 is preferably disposed in contiguous relationship to apinch roller 100 so that the tension of the tape is precisely regulatedwhen the tape becomes disposed on the periphery of the pinch roller. Theguide 52 (FIGS. 12-13) is coupled as by bolts 98 to a pinch rollerassembly generally indicated at 96. The pinch roller assembly 96includes the pinch roller 100. The guide 52 is adjustably positionedrelative to the pinch roller 100 as by a pair of eccentrics 104 and 106(FIGS. 12, 12A, 12B and 13). The eccentric 104 may be operative to movethe guide 52 vertically in accordance with the rotation of theeccentric. The eccentric 106 may be operative to move the guide 52vertically so as to adjust the tilt of the guide relative to the pinchroller 100. It is believed that the construction of eccentrics such asthe eccentrics 104 and 106 are well known to persons of ordinary skillin the art. Furthermore, the construction of the eccentric 106 maycorrespond to the construction of the eccentric shown in FIGS. 24-26.Although the construction of the eccentrics 104 and 106 is considered tobe well known in the art, the use of such eccentrics in a pinch rollerassembly is not believed to be known in the art.

The pinch roller 100 may be molded on a shaft 108 and may be constructedfrom a suitable material such as a polyurethane. Polyurethane is adesirable material because it has very good wear characteristics andbecause it takes only a minimal permanent set from continued pressurefrom a capstan abutting the pinch roller in the operative relationshipof the pinch roller and the capstan. Polyurethane is also desirable fromthe standpoint of its ability to adhere to the shaft 108 and also fromthe standpoint of having a low hysteresis in resisting the effects ofheat. A suitable polyurethane for use as the pinch roller 100 may beobtained from Harkness in Bristol, Conn. This polyurethane may have ahardness of 60 Shorr on the A scale.

The shaft 108 is supported in a bearing 110 (FIG. 13 and 14) on asupport plate 112 which is supported on a knuckle support 114 (FIG. 13).The support plate 112 is precisely positioned on the knuckle support 114as by pins 116 and is then secured to the frame as by threaded bolts118. A bearing plate 120 is secured to the top of the support plate 112as by a threaded bolt 122. The bearing plate 120 is provided with lugs124 (FIG. 14) which extend downwardly and engage the bearing 110 tocreate a force having axial and radial components on the bearing, theradial component of the force being directed inwardly toward the shaft108. This force prevents the pinch roller 100 from being off-round asthe pinch roller 100 rotates and presses against the capstan during suchrotation. This force also prevents axial displacement of the pinchroller 100. The polyurethane pinch roller 100 is also preferably groundon centers to obtain a run-out of less than two ten-thousandths of aninch (0.0002").

The attention devoted to the pinch roller 100 and the supportingstructure as discussed above assures that the pinch roller 100 will notwobble as it rotates. Wobbling of the pinch roller 100 is undesirablebecause it creates inaccuracies in the transfer of magnetic informationfrom the master tape 10 to the thermomagnetic layer 14 on the slave tape12. The pinch roller 100 is rotated by the capstan as a result oftension between the master tape 10 and the slave tape 12.

The pinch roller assembly 96 includes a base member 126 (FIGS. 12-13 and15) extending from the bottom of the frame 114. The member 126 has ahole 130 for receiving a positioning knuckle 132 (FIG. 15) to providefor a rotation of the knuckle support 114 on the knuckle 132. The basemember 126 forms a part of a frame 133. The knuckle support 114 ispivotably secured to the frame 133 as by a pivot pin 134 (FIGS. 12B and13). An adjustable screw 135 (FIG. 23) is disposed on a post 137 toadjust the position of the knuckle 132 (FIG. 15).

A lug 136 (FIG. 15) extends from the bottom of the knuckle support 114and cooperates with a recess 138 (FIG. 16) in a positioning member 139of a capstan assembly generally indicated at 140 to define a detentarrangement with the recess for locking the pinch roller assembly 96 tothe positioning member 139. A bearing 142 (FIG. 15) on the end of thepinch roller shaft 108 is disposed in a slot 144 in a support plate 145to facilitate the movement of the pinch roller assembly 96 into lockingrelationship with the capstan assembly 140. The pinch roller 100 and theguide 52 may be moved manually between the withdrawn position and theextended position or they may be moved by an actuator 157 (FIG. 1). Theactuator 157, the vacuum source 59a, the source 60a of pressurized air,the drive motor 123 and the take-up motors 20 and 26 may be operatedunder the control of a controller 159 (FIG. 1).

A guide generally indicated at 151 (FIG. 1) and having a constructioncorresponding to that of the guide 52 is associated with the slave tape12 in a manner similar to the association between the guide 52 and themaster tape 10. The guide 151 may have a construction corresponding tothat of the guide 51. However, peripheral surfaces 161 and 162 on theguide 151 preferably have less orifices 163 (FIG. 7) than the number oforifices 61 and 62 (FIGS. 4 and 6) in the peripheral surfaces 59 and 60of the guide 52 respectively receiving the vacuum and the air underpressure. This provides for a lower braking action at the peripheralsurface 161 of the guide 151 than the braking action provided at theperipheral surface 59 of the guide 52. However, depending upon thecharacteristics of the master tape 10 and the slave tape 12, the brakingaction at the peripheral surface 161 of the guide 151 may be equal to,or greater than the braking action at the peripheral surface 59 of theguide 52. The guide 151 is constructed to receive a vacuum from thesource 59 in a manner similar to the guide 52. Although the guides 52and 151 are shown as receiving a vacuum from the source 59a, it may bepreferable to use separate sources for the guides 52 and 151 to enhancethe tension controls provided by the guides.

Preferably the braking action provided at the peripheral surface 161 isless than the braking action provided at the peripheral surface 59 ofthe guide 52. This results from the fact that the slave tape 10 islengthened as the slave tape 12 is heated to a temperature above theCurie temperature just before the slave tape 12 reaches the capstan.Since the slave tape 12 is lengthened by this heat, it does not have tobe tensioned as much at the guide 151 as the tensioning of the mastertape 10 by the guide 52 in order to obtain a transfer of the informationon the master tape 10 to the slave tape 12 in what constitutes a mirrorimage after the slave tape has cooled to ambient temperatures.

The guide 151 is disposed so that the thermomagnetic layer 14 on theslave tape 12 faces outwardly from the external surface of the guide asthe slave tape moves along this external surface. As with therelationship between the guide 52 and the pinch roller 100, the guide151 is positioned close to a capstan 160 in the capstan assembly 140.Although the guide 151 is not adjustably positioned horizontally orvertically in a manner similar to that provided by the eccentrics 104and 106 (FIGS. 12 and 13) for the guide 52, such adjustments may beprovided without departing from the scope of the invention.

The capstan 160 and a shaft 161 (FIGS. 17, 18, 20, and 21) extendingfrom the capstan are preferably formed from a single composite piece ofmaterial. Preferably the capstan is built with chrome plated brassbrazed to a stainless steel shaft. The brass is desirable because it isnon magnetic and does not corrode. Chrome is desirable because it ishard and can be polished to a fine finish. The capstan 160 and the shaft161 are preferably constructed so that they have a minimal run-out. Forexample, the shaft 162 and the capstan 160 are preferably provided withan eccentricity of less than one ten thousandth of an inch (0.0001").The shaft 161 and the capstan 160 are positioned relative to a supportplate 167 in a manner similar to that provided for the shaft 108 by thepins 116 and the bolts 118.

The capstan 160 may be supported by a bearing arrangement (see FIG. 14)similar to that provided for the pinch roller 100. This arrangementincludes bearings 162 and lugs 163 (FIG. 15-18) extending from a plate164 to fixedly position the capstan 160 in the axial direction andinwardly in the radial direction. The capstan assembly 140 is providedwith a frame 165 (FIGS. 15 and 21) having a slot 166 in its base foradjustable positioning on a table (not shown) on which the capstanassembly rests. When the capstan assembly 140 has been adjusted to thedesired position, the capstan assembly is fixedly positioned on thetable by tightening screws 168 extending through the slot 166 to thetable. The capstan assembly 140 is adjustably disposed in the frame 165relative to the fixedly positioned member 139 (FIGS. 16 and 20) whichdefines at one end the recess 138 for providing the detent relationshipwith the lug 136 in the pinch roller assembly 96.

A heater generally indicated at 172 (FIGS. 22-23 and 27-28) is disposedbetween the guide 151 and the capstan 160 to receive the slave tape 12with the thermomagnetic layer 14 of the slave tape facing the heater.The heater is preferably disposed in contiguous relationship to theguide 151 and the capstan 160. The heater 172 is preferably constructedto heat only the thermomagnetic layer 14 of the slave tape 12 to atemperature above the Curie temperature. If the supporting tape wereheated to a temperature above the Curie temperature, the thermomagneticlayer 14 would tend to shrink relative to the supporting tape. Thiswould tend to cause the tape to become excessively cupped and wouldprevent the image on the master tape 10 from becoming transferredaccurately to the slave tape 12. The heater 172 is provided with arelatively short length to prevent the slave tape 12 from becomingblistered by an excessively long time of contact with the heater. Forexample, this contact between the heater 172 and the slave tape shouldpreferably not exceed five milliseconds (0.005 sec).

The heater 172 is disposed as close as possible to the capstan 160. Thethermomagnetic layer 14 on the slave tape 12 becomes heated by theheater 172 to a temperature above the Curie temperature. During the timethat the slave tape 12 moves from the heater 172 to the capstan 160, thethermomagnetic layer 14 cools somewhat. Therefore, the heater 172 heatsthe thermomagnetic layer 14 to a temperature sufficiently above theCurie temperature such that the thermomagnetic layer 14 does not coolbelow the Curie temperature until after the thermomagnetic layer 14reaches the capstan and contacts the magnetizable layer 11 of the mastertape. This causes the magnetic information on the master tape 10 to betransferred accurately to the thermomagnetic layer 14 on the slave tape12 without having to use any magnetic heads to obtain such a transfer.

Furthermore, since the temperature of the magnetizable layer 11 of themaster tape 10, after contacting the thermomagnetic layer 14 of theslave tape 12, can rise only to the average of the temperatures of themagnetizable layer 11 and the thermomagnetic layer 14 before thecontact, the characteristics of the master tape 10 are not affected evenif the magnetizable layer 11 is a thermomagnetic layer of the same typeas that of thermomagnetic layer 14.

The heater 172 is disposed in a particular relationship to the guide 151and the capstan 160. In this particular relationship, the thermomagneticlayer 14 on the slave tape 12 faces away from the external surfaces ofthe guide 151 and the capstan 160. In facing away from the externalsurface of the capstan 160, the thermomagnetic layer 14 directly abutsthe magnetizable layer 11 on the master tape 10 (see FIG. 38). In thisway, the transfer of the magnetic information on the master tape 10 tothe thermomagnetic layer 14 on the slave tape 12 is facilitated.However, the thermomagnetic layer 14 directly faces the external surfaceof the heater 172. In this way, heat can be transferred directly to thethermomagnetic layer 14 without having to pass through the backingmember supporting the thermomagnetic layer. This facilitates the heatingof the thermomagnetic layer 14 to a temperature above the Curietemperature without heating the remainder of the slave tape 12 to such ahigh temperature.

The heater 172 is relatively short and thin. In this way, thethermomagnetic layer 14 can be heated to a temperature above the Curietemperature without significantly affecting the temperature of thebacking member supporting the thermomagnetic layer. Furthermore, bymaking the heater 172 short and thin, the heater can be disposed closeto the capstan 160. This facilitates the ability of the thermomagneticlayer 14 to operate at a temperature close to the Curie temperature whenthe information on the master tape 12 is being transferred to thethermomagnetic layer. By making the heater 172 short and thin, the heatfrom the heater can be transferred to the thermomagnetic layer 14 in arelatively short period of time such as approximately two millisecond (2ms) when the slave tape is moving at a speed of approximately onehundred and fifty inches per second (150 i.p.s.). This is desirable ininsuring that only the thermomagnetic layer 14 (and not the supportingtape 12) is heated to a temperature above the Curie temperature. Bymaking the heater short and thin, the surface of the heater disposednear the capstan 160 can be made flat rather than concave as in theprior art. A flat surface has engineering advantages and issignificantly simpler to manufacture than a concave surface as in theprior art.

The heater 172 includes a support member 174 (FIGS. 31 and 33).Preferably the support member 174 is made from an insulating member suchas a ceramic. Aluminum nitride is a desirable ceramic for certainimportant reasons. One reason is that it has a low coefficient ofthermal expansion. Another reason is that it has a high thermalconductivity. In this way, the support member 174 is able to transferheat quickly and efficiently to the thermomagnetic layer 14 on the slavetape 10 without changing its physical dimensions appreciably withincreases in temperature and without a large thermal gradient. Aluminumnitride is also advantageous because it is relatively stable. Anotheradvantage of aluminum nitride is that its external surface abutting thethermomagnetic layer 14 of the slave tape 12 can be polished to a greatsmoothness so as to maximize the surface area of contact and thus theheat transfer efficiency. This external surface is indicated at 176 inFIGS. 31 and 32.

The external surface 176 of the support member 174 may define a segmentof a cylinder. This cylinder may have a radius of approximately one halfof an inch (0.5"). It is desirable that the external surface 176 definea segment of a cylinder in order to assure that pockets of air will notbe formed between the external periphery and the slave tape 12 as theslave tape moves along the internal periphery. As will be appreciated,the slave tape 12 moves in the direction of the curvature in theexternal surface of the support member 174. The maximum thickness of thesupport member 174 may have a dimension of thirty five thousandths of aninch (0.035").

As indicated at 175 (FIG. 33) at the input side of the insulating member174, the external surface 176 of the insulating support member 174 maybe rounded at its input end in the direction of movement of the slavetape 12 to provide a smaller radius than the radius at intermediatepositions on the member. This assures that the slave tape 12 will notform a gap with the external surface 176 as it initially engages theexternal surface 176 of the member 174 at the input end of the member.The formation of such a gap is undesirable since it creates air pocketswhich allow the heater to get excessively hot. The air pockets alsoprevent the thermomagnetic layer 14 on the slave tape from being heateduniformly as the slave tape moves on the external surface 176. In likemanner, the external surface 176 of the member 174 is rounded as at 177at the output end with a smaller radius than at intermediate positionson this surface. This also prevents air pockets from being producedbetween the tape 12 and the external surface 176 of the member 174 atthe output end of this surface as the slave tape 12 leaves the member.

The support member 174 has an external surface 178 (FIG. 31) oppositethe surface 176. The surface 178 is preferably flat. As a first step informing the heater 172, the support member 174, when formed fromaluminum nitride, may be heated to an elevated temperature such asapproximately 950° C. in air for a suitable period of time such asapproximately two (2) hours. This causes a coating of aluminum oxide tobe produced on the external surfaces of the support member 174. Thiscoating of aluminum oxide appears to be desirable in retaining thecoatings of materials subsequently deposited on the surfaces of thesupport member 174.

After the formation of the aluminum oxide on the surface 178 of thesupport member 174, the surface is subsequently cleaned thoroughly. Alayer 180 (FIGS. 31 and 32) of titanium is then deposited on thissurface in a suitable thickness such as approximately one thousandAngstrom (1000 Å). Titanium has good heat conductivity and a lowcoefficient of thermal expansion. Then a layer 182 of platinum having athickness such as approximately four thousand Angstrom (4000 Å) isdeposited on the titanium. The titanium layer 180 is desirable betweenthe surface 178 of the support member 174 and the platinum layer 182because titanium has an affinity for aluminum nitride, aluminum oxideand platinum.

The platinum layer 182 is then annealed at a suitable temperature suchas approximately 750° C. for a suitable period of time such asapproximately fifteen (15) minutes to soften the platinum. The platinumlayer 182 is then cooled at a suitable rate such as approximately threecentigrade degrees (3° C.) per minute to room temperature. Thisannealing of the platinum layer 182 prevents the platinum from crackingwhen heat and stress are imposed upon the heater 172. It also avoids anyproblems in the platinum when one side of the heater 172 is at adifferent temperature than the other side of the heater.

A layer of gold having a suitable thickness such as 200 micro inches(0.0002 inch) is then deposited as by plating on the platinum. The goldin the laterally middle portion of the layer is then removed to definetwo (2) terminals 190 and 192 (FIG. 32). The layers 190 and 192 ofplated gold define the terminals for receiving an electrical voltage.This voltage is introduced to the gold layer 190 and 192 by straps 193(FIG. 23) made from a suitable material such as gold-plated copper. Thisvoltage produces a flow of current through the platinum layer 182 forheating the platinum layer. The platinum layer has a greater thicknesson the input side (in the direction of movement of the slave tape 10) ofthe heater than on the output side of the heater, as indicated on anexaggerated basis at 194 in FIG. 33. In this way, the platinum 194 layerdevelops more heat on the input side of the heater than on the outputside of the heater. This is desirable in insuring that the temperaturein the thermomagnetic layer 14 of the slave tape 12 is brought quicklyabove the Curie temperature.

Preferably, the input side of the platinum layer 182 may provide agreater amount of power than the output side of the platinum even with auniform thickness of the platinum layer. This results from the coolingof the platinum layer by the slave tape 12 as the slave tape contactsthe heater. This causes the resistance of the platinum layer at theinput side to be lower than the resistance of the platinum layer at theoutput side because the temperature coefficient of resistivity ofplatinum is positive. Such differences in resistance value cause thepower generated at the input side of the platinum layer to be greaterthan the power generated at the output side of the platinum layer.

The distance between the gold terminals 190 and 192 is preferablygreater by a particular distance than the lateral width of the slavetape 12. In this way, the thermomagnetic layer 14 on the slave tape 12is heated substantially uniformly across the lateral width of the slavetape. With an optimum distance between the inner ends of the terminals190 and 192 and the lateral peripheries of the slave tape 12, theplatinum is able, in the distance between the inner ends of theterminals and the lateral peripheries of the slave tape, to heat thelateral peripheries of the thermomagnetic layer 14 on the slave tape 12by an optimal amount. This causes the lateral peripheries of thethermomagnetic layer 14 on the slave tape 12 to be maintained atsubstantially the same temperature as the remainder of thethermomagnetic layer. If the distance between the inner ends of theterminals 190 and 192 and the lateral peripheries of the slave tape 12is too great, the lateral peripheries of the thermomagnetic layer 14 onthe slave tape 12 may tend to become overheated relative to theremainder of the thermomagnetic layer. If this distance is too small,the lateral peripheries of the thermomagnetic layer 14 on the slave tape12 may tend to become underheated relative to the remainder of thethermomagnetic layer.

When the thermomagnetic layer 14 of the slave tape 12 is moved along theexternal surface 176 of the support member 174, the external surface 176tends to accumulate an electrostatic charge. This electrostatic chargeis undesirable since it tends to interfere with the movement of theslave tape by causing a stretching of the tape. To eliminate thiselectrostatic charge, the external surface 176 of the support member 174may be initially coated with a layer 195 (FIG. 34) of titanium having asuitable thickness such as approximately five hundred Angstrom (500 Å).A layer of an electrically conductive material such as gold 196 having asuitable thickness such as approximately eight thousand Angstrom (8000Å) may then be deposited as by sputtering on the titanium layer. A layerof gold 198 having a suitable thickness such as approximately one mil (1m) may thereafter be deposited as by plating on the gold layer 196. Thelayers 194, 196 and 198 are connected to electrical ground and areeffective in dissipating electrostatic charges as such electrostaticcharges are formed by movement of the slave tape 10 on the externalsurface 176 of the member 174.

The heater 172 is included in a heater assembly generally indicated at200 (FIGS. 22 and 23). The heater assembly 200 includes a pair of holderassemblies generally indicated at 202 (FIG. 22). The holder assemblies202 are disposed at the top and bottom of the heater 172 to hold theheater in a fixed position. Each of the holder assemblies 202 includes apair of positioning members 204 and 206 (FIG. 27) which are clamped toeach other as by threaded bolts 208 (FIG. 27). The positioning members204 and 206 define an internal socket 193 (FIG. 27) for receiving theheater 172. The socket 193 is slightly oversized relative to the heater172 to provide for any expansion of the heater with heat. Spacers 205(FIGS. 22 and 23) made from a material providing a low heat transfer aredisposed adjacent the positioning members 204 and 206 to limit thetransfer of heat from the positioning members.

A pair of springs 212 (FIG. 27) are disposed between the positioningmembers 204 and 206 at the opposite ends of the heater 172 and aredisposed on the heater 172 to support the heater in a fixed positionwithin the socket 193. The springs 212 may be made from a suitablematerial such as Inconel 718. Inconel 718 is desirable because it hasgood properties at high temperatures and because it does not take apermanent set when heated. The springs 212 are disposed in the internalsocket 193 so as to be expansible with increases in temperature. Thesprings 212 may initially be flat and may be deformed as shown in FIG.27 when they are disposed on the heater 172. The springs 212 may beprovided with an extended slot 213 to provide for expansion relative tothe heater 172 and the positioning members 204 and 206.

The heater assembly 202 also includes a pair of bridge members 214 (FIG.22) which are attached to the heater assembly 200 as at 216 to positionthe heater 172 in facing relationship with the thermomagnetic layer 14on the slave tape 12. A shaft 216 (FIG. 24) extends through the bridgemembers 214 and a support plate 219 to provide for a pivotal movement ofthe heater 172 to a position abutting the thermomagnetic layer 14 on theslave tape 12 or to a position displaced from the slave tape. When theheater 172 is displaced from the slave tape 12, the disposition of theslave tape on the guide 151 and the capstan 160 can be facilitated. Theheater 172 becomes displaced from the slave tape 12 as by a spring 215(FIG. 22) which is attached at one end to the heater assembly 200 and atthe other end to a fixed post 223. A leaf spring 221 (FIGS. 17 and 18)acts to move the heater assembly toward the capstan 160 as the pinchroller extends.

As shown in FIGS. 24-25, an eccentric 218 is disposed within the supportplate 219. As the eccentric 218 is turned, the shaft 216 is moved in aslot 220 (FIG. 26) so as to tilt the heater 172 horizontally. Apositioning pin 222 (FIGS. 24 and 25) is threaded in a hole 224 in thesupport plate 219 to lock the eccentric 218 after the eccentric has beenturned to the desired position. An insert 226 (FIG. 26) is disposed onthe shaft 216 at a position below the eccentric 218. A Belleville spring228 (FIG. 24) is disposed on the shaft 216 between the insert 226 and aspacer 230 (FIGS. 23 and 24) to hold the insert 226 against theeccentric 218 for maintaining the position of the heater assembly.Electrical insulators 229 and 231 electrically isolate the upper andlower bridge members 214. Electrical terminals 230 (FIGS. 23 and 24) areprovided on an insulating block 234 disposed between the bridge members214 at the end of the bridge members opposite the heater 172. Theterminals 230 hold the ends of the straps 193 opposite the heater 172.Electrical leads 236 extend from the terminals 230 to a voltage source(not shown) for producing a current through the platinum layer 182(FIGS. 31 and 32) or the platinum layer 194 (FIG. 33) to heat theheater.

The heater 172 is locked in position between two opposite pins when itis disposed to receive the slave tape 12 moving from the guide 151 tothe capstan 160. One of the pins is disposed on the pinch rollerassembly 96 at a position below the guide 151 and is indicated at 240 inFIGS. 12A and 36. The other pin is indicated at 242 in FIGS. 21, 35 and36 and is adjustably threaded in a fixed support member 244 in FIGS. 35and 36. The pin 242 is fixedly retained in the support member 244 as bya nut 246. The pins 240 and 242 respectively bear against the oppositesurfaces of the lower holder assembly 202. When the heater 172 ispositioned between the pins 240 and 242, it still has a slightadjustability such as in the order of a few mils. This provides for afixed and precise positioning of the slave tape 12 on the heater 172while still providing for a slight adjustment in this precisepositioning.

In order to position the master tape 10 properly on the pinch roller 100and the slave tape properly on the capstan 160, the pinch rollerassembly 96 is moved to a position where the pinch roller is displacedfrom the capstan 160. The guide 52 is also movable with the pinch roller100 to the position displaced from the capstan 160. With the pinchroller 100 and the guide 52 in the displaced positions, the slave tape12 can be disposed on the capstan 160. The positioning of the slave tape12 on the capstan 160 is facilitated by the pivotal movement of theheater assembly 200 away from the capstan on the shaft 216 (FIG. 24) asa fulcrum. The movement of the heater assembly 200 away from the capstanis provided by the spring 215 in FIG. 22. After the slave tape 12 hasbeen disposed on the capstan 160, the heater assembly 200 can bereleased. The heater 172 will then return to the position where it abutsthe thermomagnetic layer 14 on the slave tape 12. This is provided bythe spring 221 (FIG. 17).

When the slave tape 10 has been disposed on the guide 151, the heater172 and the capstan 160, the bevelled surface and the ledge of the guide151 corresponding to the bevelled surface 50 (FIG. 9) and the ledge 53on the guide 52 position the slave tape so that the slave tape moves toa particular position on the capstan 160. If the slave tape 12 does notmove to the particular position on the capstan 160, the position of theguide 151 can be adjusted vertically in accordance with adjustments inan eccentric on the guide 151 corresponding to the eccentric 104 (FIGS.12 and 13). The position of the guide 151 can also be adjustedvertically, as by a tilting motion, by adjusting an eccentric in theguide 151 corresponding to the eccentric 106 (FIGS. 12, 12A, 12B and 13)in the guide 52. In the embodiment constructed, eccentrics correspondingto the eccentrics 104 and 106 on the guide 52 were not provided on theguide 151. However, it will be appreciated that such eccentrics can beprovided on the guide 151 without departing from the scope of theinvention.

The heater 172 can be tilted by adjusting the position of the eccentric218 (FIGS. 24-25) in the heater assembly 200. Since the heater 172 isdisposed relatively close to the capstan 160, the adjustment provided bythe eccentric 218 can be considered to provide a fine control over thepositioning of the slave tape 12 on the capstan. In this way, themovement of the slave tape 12 to the capstan 160 can be controlled sothat the slave tape has a precise position on the capstan. This isimportant in insuring that a precise transfer of information is providedfrom the master tape 10 to the thermomagnetic layer 14 on the slave tape12 at the abutting positions of the pinch roller 100 and the capstan160.

The master tape 10 is disposed on the guide 52 and the pinch roller 100while the guide and the pinch roller are displaced from the capstan 160.The guide 52 and the pinch roller 100 are then moved to a position wherethe pinch roller abuts the capstan. At the end of this movement, thepinch roller 100 becomes locked to the capstan 160 by the lockingarrangement between the lug 136 (FIGS. 12, 12A and 12B) on the pinchroller assembly and the recess 138 (FIG. 16) in the capstan assembly140. When the pinch roller 100 becomes locked to the capstan 160, theheater 172 also becomes locked into position (except for a slight playof a few thousands of an inch) by the pin 240 (FIGS. 12A and 36) on thepinch roller assembly 96 and by the adjustably positioned pin 242 (FIGS.35 and 36).

The master tape 10 is precisely positioned on the pinch roller 100 bythe inclined surface 50 (FIG. 9) and the ledge 53 on the externalsurface of the guide 52. The inclined surface 50 and the ledge 53 causethe master tape 10 to become positioned on the ledge 53 as the mastertape 10 moves along the guide 52. The position of the master tape 10 onthe pinch roller 96 can be further adjusted by adjusting the eccentrics104 and 106 (FIGS. 12, 12A, 12B and 13). The eccentric 104 provides avertical adjustment in the position of the guide 52 and the eccentric106 provides a horizontal adjustment in the position of the guide albeitat a position displaced from the eccentric 104. Thus the eccentric 104and the eccentric 106 in combination provide an adjustment of the heightand the tilt of the guide 52. In this way, the master tape 10 can bedirected to a position on the pinch roller 100 precisely correspondingto the position of the slave tape 12 on the capstan 160.

As will be appreciated, the master tape 10 is strained in one directionby the bevel or incline in the surface 50 (FIG. 9) in the guide 52. Thisstrain in one direction is compensated in the other direction by the pin48 (FIGS. 1 and 11). In like manner, the pin 154 compensates for thestrain imposed on the slave tape 12 by the bevel in the surface of theguide 151 corresponding to the inclined surface 50 in the guide 52.

The guide 52 regulates the tension of the master tape 10 at a positioncontiguous to the pinch roller 100. In like manner, the guide 151regulates the tension of the slave tape 12 at a position contiguous tothe capstan 160. These regulations of tape tension provide for atransfer of the video information on the tape 10 to the thermomagneticlayer 14 on the slave tape 12 in a mirror image with greater fidelity,this mirror image being provided after the slave tape has cooled toambient temperature. This precise transfer is facilitated by theconstant characteristics provided for the master tape 10 and for theslave tape 12. As will be appreciated, however, the constantcharacteristics provided for the master tape 10 may be different fromthe constant characteristics provided for the slave tape 12. Thisresults from the fact that the regulated tension on the master tape 10may be greater than the regulated tension provided on the slave tape 12because of the expansion of the slave tape 12 by the heat from theheater 172 just before the slave tape reaches the capstan 160.

As will be appreciated, the guide 151 performs the same function on theslave tape 12 as the guide 52 performs on the master tape 10. However,the guide 151 for the slave tape 12 can have less orifices 163 on itsperipheral surface 161 than the number of apertures 61 (FIG. 4) at theperipheral surface 59 of the guide 52 for the master tape 10. This maybe seen from a comparison of FIGS. 6 and 7. The increased braking actionprovided by the guide 52 relative to that provided by the guide 151results from the fact that the slave tape 12 is expanded by the heater172 as it moves over the heater. In effect, the increased braking actionof the guide 52 stretches the master tape 10 to conform to the expansionprovided on the slave tape 12 by the heater 172.

Since each of the guides 52 and 151 has orifices which are covered bythe respective ones of the tapes 10 and 12, very little air flowsthrough the peripheral surfaces 59 and 161 which provide the brakingaction on the respective tapes. Therefore, the vacuum source 59a can besmall and can have a low capacity. For example, a diaphragm type ofaquarium pump can be used as the vacuum source 59a. A "Supra 4" pumpdistributed by Willinger Brothers of Wrightway Oakland, N.J., has beenfound satisfactory for use as the vacuum source 59a but a number ofother pumps can also be used. This pump is designed as a pressure pump.It can be easily modified to provide a vacuum source by reversing theinlet and outlet ports and adjusting the diaphragm position.

FIG. 39 is a schematic block diagram of a system for regulating the heatproduced by the heater 172 and for providing an almost instantaneousheating of the heater on a regulated basis when the apparatus shown inFIGS. 1-38 initially becomes operative. The system shown in FIG. 39includes a potentiometer 280 having an adjustable arm 282. The voltageon the adjustable arm 282 is introduced to a circuit 284 whichmultiplies the adjustable voltage by a transfer function such as a timeconstant to obtain a signal representing the desired amount of power tobe introduced to the heater 172.

The signal from the time constant circuit 284 is introduced to adifferencing circuit 286 which also receives a signal input from awattmeter 288. The output from the differencing circuit 286 isintroduced to an integrator 290. The output from the integrator 290 inturn passes to a stage 292 for obtaining a square root of the outputfrom the integrator. The output from the square root stage 292 thenpasses to a multiplier 294 which also receives a signal on a line 296.The signal on the line 296 is an alternating signal having a particularwaveform such as a sine wave or a square wave. A power amplifier 298receives the output signal from the multiplier 294 and introduces anamplified signal to the heater 172. The input current and voltage to theheater are introduced to the wattmeter 288.

As will be seen, the system shown in FIG. 39 constitutes a closed loopservo for regulating the power introduced to the heater 172 inaccordance with a desired amount of power represented by the voltage onthe adjustable arm 282 of the potentiometer 280. This voltage is variedby the time constant provided by the stage 284. The resultant signalrepresents the desired power to be introduced to the heater 172.

The resultant signal from the stage 284 is introduced to the comparator286 for comparison with the signal from the wattmeter 288. The signalfrom the wattmeter 288 represents at each instant the amount of powergenerated by the heater 172 at that instant. The output from thedifferencing circuit 286 accordingly represents at each instant anydifference between the desired power and the actual power introduced tothe heater 172 at that instant.

The difference signal from the differencing circuit 286 is introduced tothe integrator 290 which integrates the difference signal at progressiveinstants of time. The output from the integrator 290 is introduced tothe stage 292 which determines at each instant the square root of theoutput from the integrator 290. The output from the stage 292accordingly represents the power introduced to the heater 172 at thatinstant.

The square root output from the stage 292 is in the form of a variabledirect voltage. This signal is introduced to the multiplier 294 formultiplication with an alternating signal, such as a sine wave signal ora square wave signal, on the line 296. The resultant alternating signalis amplified by the amplifier 298 and the amplified signal is introducedto the heater 172.

In this way, the heat produced in the heater 172 at each instant isregulated in accordance with a desired amount of heat as represented bythe voltage on the adjustable arm 282 of the potentiometer 280. Thesquare root function 292 assures that the power into the heater is alinear function of the position of the potentiometer arm 282. Withoutthe square root function 292, relatively small changes in the positionof the potentiometer arm 282 at typical operating powers will causelarge changes in the heater power. It will be appreciated that thepotentiometer 280 can be replaced by other command means such as adigital-to-analog converter connected to a microprocessor. The systemshown in FIG. 39 and discussed above provides this regulation on aninstantaneous basis. For example, this regulation is provided in lessthan a second after the slave tape 12 starts to move.

The time constant stage 284 and the integrator 290 may be caged whilethe system shown in FIGS. 1-38 is not in use. When the time constantstage 284 and the integrator 290 are caged, a low amount of power isintroduced to these stages to prepare the system shown in FIG. 39 forinstantaneous operation when the transfer of information from the mastertape 10 to the slave tape 12 is initiated. When the transfer ofinformation from the master tape 10 to the slave tape 12 is initiated,the time constant stage 284 and the integrator 290 are uncaged.

The system described above has a number of important advantages. Itprovides a precise transfer of an image on a mirror basis from themaster tape 10 to the slave tape 12 after the slave tape has cooled toambient temperatures. It provides this precise transfer in a minimalperiod of time. For example, a two (2) hour tape of a movie can betransferred from the master tape 10 to the slave tape 12 in a period ofapproximately thirty (30) seconds. The system is also advantageous inthat the master tape 10 can be disposed easily on the pinch roller 100and the guide 52 associated with the pinch roller and the slave tape canbe disposed easily on the capstan 160, the associated guide 151 and theheater 172. This is important when images are being transferred from themaster tape 10 to the slave tape 12 on a commercial basis where time isimportant. The system is further advantageous in that the information onthe master tape 10 can be transferred to the slave tape 12 withouthaving to use any reading or recording heads.

The system of this invention also has other important advantages. Forexample, when the slave tape 12 has the thermomagnetic layer 14, thesystem of this invention heats essentially only the thermomagnetic layerto a temperature above the Curie temperature. This is important inconserving power and in preserving the characteristics of the slave tape12 for subsequent use and in providing an accurate transfer ofinformation from the master tape 10 to the slave tape 12. The systemincludes members for maintaining the tension on each of the master andslave tapes substantially constant. This enhances the accuracy in whichthe information on the master tape 10 is transferred to the slave tape12. The system of this invention maintains the tensions on the tapessubstantially constant and damps any variations in the tape tensions.The system accomplishes this by regulating the tension of the mastertape 10 at a position contiguous to the pinch roller 100 and byregulating the tension of the slave tape 10 at a position contiguous tothe heater 172.

There are other important advantages to the system of this invention.This results from the construction and operation of the guide member 52in disposing the master tape 10 on the guide member to position themaster tape precisely at a particular position on the pinch roller 100.It also results from the adjustability of the guide member 52, bothvertically and with regard to its slope, to assure that the master tape10 moves precisely to the particular position on the pinch roller 100.

The guide 151 may be constructed and may be adjustable in the samemanner as the guide member 52 to position the slave tape 12 precisely ata particular position on the capstan 160 corresponding to the particularposition on the pinch roller 100. If there is any deviation between theparticular positions on the pinch roller 100 and the capstan 160, theposition of the slave tape 12 on the capstan 160 can be fine tuned byadjusting the position of the heater 172 so that the position of themaster tape 10 on the pinch roller 100 and the position of the slavetape 12 on the capstan 160 coincide.

The construction of the heater 172 and the disposition of the slave tape12 on the heater are also advantageous. For example, the slave tape 12is disposed relative to the heater 72 so that the thermomagnetic layer14 on the slave tape 12 abuts the surface of the heater. Furthermore,the external surface of the heater 172 is shaped to prevent any airbubbles from lifting the slave tape 12 from the heater. The heater 172is also formed from materials which assure an optimal operation of theheater. The heater 172 is also pivotable to a position displaced fromthe path of the slave tape to facilitate the disposition of the slavetape on the heater and the capstan 160 and disposition of the mastertape 10 on the pinch roller 100.

The invention also provides other advantages of some importance. Itincludes features for precisely regulating the tension of the mastertape 10 just before the movement of the master tape to the surface ofthe pinch roller 100. It also includes similar features for preciselyregulating the tension of the slave tape 12 just before the movement ofthe slave tape to the surface of the heater 172, which is disposed incontiguous relationship to the capstan 160. The system of the inventionprovides these regulations of tape tension in a way to compensate forthe stretching of the slave tape 12 by the heat from the heater 172.

There are even other important advantages in this invention. Forexample, the master tape 10 can be manufactured with certain specificconstant characteristics (including the product of Youngs modulus,thickness and width) so that the mechanism regulating the tension of themaster tape 10 never has to be adjusted even when master tapesmanufactured at different times in different batches are used.Similarly, the slave tape 12 can be manufactured with certain specificconstant characteristics (including the product of Youngs modulus,thickness and width) so that the mechanism regulating the tension of theslave tape 12 never has to be adjusted even when slave tapesmanufactured at different times in different batches are used. As willbe appreciated, the product of the Youngs modulus, thickness and widthfor the characteristics of the master tape 10 can have a different valuethan the product of the Youngs modulus, thickness and width for thecharacteristics of the slave tape 10 to compensate for the stretchingproduced in the slave tape by the heater 172.

The guide 52 has been described as being in contiguous relationship tothe pinch roller 100. It will be appreciated, however, that the guide 52may be disposed at any distance from the pinch roller 100 withoutdeparting from the scope of the invention and that the guide at thesevariable positions will still regulate the tension of the master tape 10at the pinch roller 100 as described previously in this specification.Similarly, the guide 151 may be varied from a position contiguous to theheater 172 without departing from the scope of the invention.

It will also be appreciated that the guide 52 may be used with anystretchable medium to regulate the tension of such medium and that themaster tape 10 is one form of such a medium. For example, the guide 52may be used to regulate the tension of belts and pulleys. It will alsobe appreciated that such media may provide other transducing actionsthan the transfer of magnetic information between the master tape 10 andthe slave tape 12. In like manner, the slave tape 12 constitutes onlyone form of stretchable medium which may be used in this invention, andthe tension of such medium may be regulated as described above withoutdeparting from the scope of the invention.

As shown above in equations 11, 12 and 13, stretching of a tape is afunction of the tape width, the tape thickness and the Youngs modulus ofthe tape. This can be used to regulate the force preset in the spring 66in FIG. 5. As a first step in accomplishing this, the system shown inthe drawings and described above runs the tape such as the master tape10 at a tension T1 from the beginning of the tape to the end of thetape. The angle of rotation of the pinch roller 100 to provide such atape movement is measured by a meter 300 in FIG. 43. If the radius ofthe capstan is R1 and the angle of rotation of the pinch roller 100 isβ1 radians, the tape length L1 from the beginning to the end of the tapeis

    L1=R1β1                                               (16)

The tape such as the master tape 10 is again run from beginning to endwith the tape at a tension T2. The angle of rotation of the tape 10 asmeasured by the meter 300 is

    L2=R1β2 where                                         (17)

β2 is the angle of rotation of the pinch roller and L2 is the length ofthe tape.

The change in the strain on the tape between the two (2) tape rotationsis

    Δe=(L2-L1)/L2=(β2-β1)/β2              (18)

By measurement, the change in tension is

    ΔT=T2-T1                                             (19)

Therefore,

    Δe/ΔT=(β2-β1)/(β2(T2-T1))=EWd

This relation of Δe/ΔT to obtain EWD may be seen from equation 13.

Since EWd (the product of tape width, tape thickness and Youngs modulus)can be determined in this manner, the tension T for such tape can bepreset to obtain a desired strain e in accordance with the formulaspecified in equation 13 and repeated below as

    e=T/EWd                                                    (13)

The tension T can be preset by adjusting the constraint of the spring 66in FIG. 5. The constraint of the spring 66 is adjusted by adjusting thescrew 67 in FIG. 5.

All of the operations discussed in the previous paragraphs can beaccomplished by the apparatus shown in FIG. 43. For example, amicroprocessor 302 can instruct an adjusting mechanism 304 to adjust thescrew 67 in FIG. 5 to obtain the tension T1, and then to obtain thetension T2, in the tape 10. The microprocessor can then determine thechange in the tension, ΔT, from the values set for the tension values T1and T2. The microprocessor 302 can also use the measurements obtainedfrom the meter 300 to determine the value of (β2-β1)/β2(T2-T1), thisvalue being representative of the product of the width, thickness andYoungs modulus of the master tape. From this determination, themicroprocessor 302 can then calculate the tension to be applied to themaster tape 10 to produce a desired strain in the tape. Themicroprocessor 302 can then instruct the adjusting mechanism 304 toproduce the proper constraint in the spring 66 in FIG. 5 for theproduction of the desired strain in the master tape 10.

It will be appreciated that the system shown in FIG. 43 and discussedabove works as effectively in determining the characteristics of a slavetape 12 with unknown characteristics as in determining thecharacteristics of a master tape 10 with unknown characteristics. Thesystem shown in FIG. 43 and discussed above also works as effectively inpresetting the strain or tension of the slave tape 12 as in presettingthe strain or tension of the master tape 10. The system also operates aseffectively in presetting the strain or tension of any stretchablemedium.

Although this invention has been disclosed and illustrated withreference to particular embodiments, the principles involved aresusceptible for use in numerous other embodiments which will be apparentto persons skilled in the art. The invention is, therefore, to belimited only as indicated by the scope of the appended claims.

We claim:
 1. In combination for operating upon a medium havingstretchable characteristics to vary the tension in the medium, themedium having a width, a thickness and a Youngs modulus and having aparticular product of the width, thickness and Youngs modulus of themedium,a guide surface, means for providing a source for the medium,means for providing a receptacle for the medium, means for driving themedium from the source to the receptacle, means for passing the mediumover the guide surface during the movement of the medium from the sourceto the receptacle, means for producing a variable fluid pressure betweenthe medium and the guide surface sufficient to separate the medium fromthe guide surface, and means disposed relative to the guide surface forregulating the tension of the medium in accordance with the variationsin the fluid pressure and in accordance with the particular product ofthe width, thickness and Youngs modulus of the medium to regulate theseparation between the medium and the guide surface.
 2. In a combinationas set forth in claim 1,guide means having a peripheral surface, theguide surface constituting the peripheral surface of the guide means,the guide means being constructed to produce the variable fluid pressureon the peripheral surface of the guide means, and the peripheral surfaceof the guide means being convex.
 3. In a combination as set forth inclaim 2,the guide means being constructed to provide a hollow interiorand the peripheral surface having orifices communicating with the hollowinterior to provide for the flow of the fluid through the hollowinterior and the orifices and the medium being disposed to receive thefluid flowing through the orifices for a separation of the medium fromthe peripheral surface of the guide means by a distance dependent uponthe pressure of the fluid passing through the orifices.
 4. Incombination for operating upon a medium having stretchablecharacteristics to vary the tension in the medium,a guide surface, meansfor providing a source for the medium, means for providing a receptaclefor the medium, means for driving the medium from the source to thereceptacle, means for passing the medium over the guide surface duringthe movement of the medium from the source to the receptacle, means forproducing a variable fluid pressure between the medium and the guidesurface sufficient to separate the medium from the guide surface, andmeans disposed relative to the guide surface for regulating the tensionof the medium in accordance with the variations in the fluid pressure toregulate the separation between the medium and the guide surface, therebeing an image on the medium, the image on the medium being in magneticform and the medium being a master tape and the image on the master tapebeing transferred to a slave tape, a pinch roller disposed after theguide surface in the direction of movement of the master tape, and acapstan disposed in abutting relationship to the pinch roller forreceiving the slave tape to provide a transfer of the magneticinformation on the master tape to the slave tape.
 5. In combination foroperating upon a medium having stretchable characteristics to vary thetension of the medium, the medium having a particular product of mediumwidth, medium thickness and Youngs modulus,first means for holding themedium, second means for holding the medium, third means for driving themedium from the first means to the second means, guide means having aperipheral surface defining a segment of a cylinder, fourth means formaintaining the medium at a variable distance from the periphery of theguide means, and fifth means for regulating the tension of the medium inaccordance with the particular product of the width, the thickness andthe Youngs modulus of the medium and in accordance with the fourth meansand the variation in the distance of the medium from the periphery ofthe guide means.
 6. In a combination as set forth in claim 5,theperipheral surface of the guide means having a radius and an axis, thefifth means being constructed to maintain a particular radial spacingbetween the medium and the axis of the peripheral surface of the guidemeans in accordance with the fourth means and the particular product ofthe thickness, width and Youngs modulus of the medium, therebyregulating the tension of the medium.
 7. In a combination as set forthin claim 6,the medium being a master tape for transferring an image onthe master tape to a slave tape, a pinch roller disposed between thefirst means and the second means, a capstan disposed in abuttingrelationship to the pinch roller, the slave tape being positionable onthe capstan for a pressing contact with the master tape to obtain atransfer of the image on the master tape to the slave tape, and meansfor driving the slave tape for movement on the capstan past the pinchroller.
 8. In a combination as set forth in claim 7,the guide meansbeing disposed relative to the pinch roller and being shaped to guidethe master tape to the receiving surface of the pinch roller, and meanson the guide means for guiding the movement of the master tape to aparticular position on the pinch roller to assure the transfer of theinformation on the master tape to precise positions on the slave tape.9. A method of regulating the tension on a stretchable medium, includingthe steps of:providing a medium extending continuously in a longitudinaldirection and having first and second spaced and parallel surfaces andhaving a width and a thickness and a Youngs modulus and having aparticular product of the width, thickness and Youngs modulus to providethe medium with a particular strain when the medium is subjected to afirst force on the medium in a direction substantially parallel to thefirst surface of the medium, the medium having properties of becomingstretched in accordance with the stress imposed upon the medium,providing a second variable force on the first surface of the medium indirections substantially perpendicular to the first surface of themedium, providing a third retarding force on the medium substantially inthe direction opposite to the direction of the first force, varying thethird retarding force on the medium in accordance with the second forceon the first surface of the medium and the particular product of thewidth, thickness and Youngs modulus of the medium to obtain a regulationof the tension of the medium, providing a movement of the medium in aparticular direction past the position at which the third retardingforce is regulated.
 10. A method as set forth in claim 9, including thestep of:the medium constituting a master tape including a backing memberand a magnetizable material on a surface of the backing member in asubstantially uniform thickness across the width of the backing member,and providing a transducing action of magnetic information between themagnetizable material on the backing member of the master tape and amagnetizable layer on a slave tape disposed in abutting relationship tothe master tape after the regulation of the tension of the master tape.11. A method as set forth in claim 9 whereinthe particular product ofthe width, thickness and Youngs modulus of the medium provides for aparticular strain with variations in the second force imposed on thefirst surface of the medium in the direction perpendicular to the firstsurface and wherein the tension of the medium is regulated at aparticular value in accordance with the variations in the second forceimposed on the first surface of the medium in the directionperpendicular to the first surface of the medium.
 12. A method as setforth in claim 9 whereinthe medium constitutes a backing member and alayer of a thermomagnetic material and the backing member and the layerof the thermomagnetic material define a slave tape and wherein thethermomagnetic layer on the slave tape has a Curie temperature abovewhich magnetic information on the thermomagnetic magnetizable layer isdestroyed and below which thermomagnetic information is recorded on themagnetizable layer and wherein heat is applied to the thermomagneticlayer of the slave tape at a position contiguous to the position atwhich the slave tape is moved on the peripheral surface of the rotarymember and wherein the variable force is applied to the first surface ofthe backing member at a position before the position at which heat isapplied to the thermomagnetic layer of the slave tape in the directionof movement of the slave tape.
 13. A method as set forth in claim 9whereinguide means is provided at a position at or before the position,in the direction of the medium, where the transducing action is providedand wherein the guide means is provided with a non-planar configurationto produce a non-planar configuration in the medium and wherein theguide means is constructed to provide a variable pressurized force atits peripheral surface in a direction perpendicular to the medium andwherein the pressurized force is regulated to control the separation ofthe medium member from the peripheral surface of the guide means.
 14. Incombination for operating upon a medium having stretchablecharacteristics to vary the tension of the medium, the medium having aparticular product of medium width, medium thickness and Youngsmodulus,first means for holding the medium, second means disposed inspaced relationship to the first means for holding the medium, thirdmeans for driving the medium from the first means to the second means,guide means having a peripheral surface, the guide means being disposedbetween the first means and the second means for receiving the medium onthe peripheral surface of the guide means during the movement of themedium from the first means to the second means, fourth means forproducing a vacuum on a first portion of the peripheral surface of theguide means, fifth means for producing a pneumatic force on a secondportion of the peripheral surface of the guide means, and sixth meansfor varying the vacuum from the fourth means in accordance with theproduct of the width, thickness and Youngs modulus of the medium and inaccordance with variations in the separation between the medium and theperipheral surface of the guide means at the second positions on theperipheral surface of the guide means to maintain such separation at aparticular value.
 15. In a combination as set forth in claim 14whereinthe first portion of the peripheral surface of the guide means isahead of the second portion of the peripheral surface of the guide meansin the direction of the movement of the medium between the first andsecond means.
 16. In a combination as set forth in claim 14 whereintheperipheral surface of the guide means defines a segment of a cylinder.17. In a combination as set forth in claim 14,the medium being a mastertape for transferring an image on the master tape to a slave tape, apinch roller disposed between the first means and the second means, acapstan disposed in abutting relationship to the pinch roller, the slavetape being positionable on the capstan for a pressing contact with themaster tape to obtain a transfer of the image on the master tape to theslave tape, and means for driving the slave tape for movement on thecapstan past the pinch roller.
 18. In a combination as set forth inclaim 14,the medium being a slave tape for duplicating an image on theslave tape from a master tape, a capstan disposed between the firstmeans and the second means, the capstan having a periphery for receivingthe medium, a pinch roller disposed in abutting relationship to thecapstan, the master tape being positionable on the pinch roller for apressing contact with the slave tape to obtain a transfer of the imageon the master tape to the slave tape, and means for driving the mastertape for movement on the pinch roller past the capstan.
 19. In acombination as set forth in claim 18,the first portion of the peripheralsurface of the guide means is ahead of the second portion of theperipheral surface of the guide means in the direction of the movementof the medium between the first and second means, the peripheral surfaceof the guide means defines a segment of a cylinder, the medium being amaster tape for transferring an image on the master tape to a slavetape, a pinch roller disposed between the first means and the secondmeans, a capstan disposed in abutting relationship to the pinch roller,the slave tape being positionable on the capstan for a pressing contactwith the master tape to obtain a transfer of the image on the mastertape to the slave tape, and means for driving the slave tape formovement on the capstan past the pinch roller.
 20. In a method ofoperating upon a medium having stretchable characteristics to vary thetension of the medium, the medium having a particular product of mediumwidth, medium thickness and Youngs modulus, the steps of:providing aguide with a peripheral surface, moving the medium along the peripheralsurface, applying a vacuum force to a first portion of the peripheralsurface on the guide, applying a pneumatic force to a second portion ofthe peripheral surface on the guide, and varying the vacuum force at thefirst portion of the peripheral surface on the guide in response tovariations in the separation between the medium and the peripheralsurface at the second portion of the peripheral surface and inaccordance with the particular product of the width, thickness andYoungs modulus of the medium to regulate at a particular value theseparation between the medium and the peripheral surface at the secondportion of the peripheral surface.
 21. In a method as set forth in claim20 whereinthe first portion of the peripheral surface is upstream fromthe second portion of the peripheral surface in the direction of themovement of the medium.
 22. In a method as set forth in claim 20whereinthe guide is hollow at its interior and is provided with orificesin its peripheral surface at the first and second portions of theperipheral surface and wherein the vacuum force is directed through theorifices in the guide at the first portion of the peripheral surface andwherein the pneumatic force is directed through the orifices in theguide at the second portion of the peripheral surface.
 23. In a methodas set forth in claim 20 whereinthe peripheral surface of the guidedefines a segment of a cylinder and wherein the vacuum and pneumaticforces are produced on the peripheral surface in a directionsubstantially perpendicular to the peripheral surface.
 24. In a methodas set forth in claim 23,the first portion of the particular surface isupstream from the second portion of the peripheral surface in thedirection of the movement of the medium, and the guide is hollow at itsinterior and is provided with orifices in its peripheral surface at thefirst and second portions of the peripheral surface and wherein thevacuum force is directed through the orifices in the guide at the firstportion of the peripheral surface and wherein the pneumatic force isdirected through the orifices in the guide at the second portion of theperipheral surface.